Load maneuvering apparatus



June l5, 1965 E. c. Fox, JR., ETAL. 3,189,195

LOAD MANEUVERING APPARATUS Filed Jan. 25, 1963 HolsT AMPLIFIER a 62 /4 0 LOWERING AMPLIFIER OPERATION/AL AMPqFlER 24o cHoPPERf/ `mz y WITNESSES= Y Ed IIVNfTCDJRS d.

gar ox1 non Rciwr'd L. Meyer.

www?? to the passive station.

United States Patent() 3,189,195 LOAD MANEUVERING APPARATUS Edgar C. Fox, .'lr., Penn Township, Allegheny County, and

Richard L. Meyer, Plum, Pa., assignors to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed Jan. 2S, 1963, Ser. No. 253,801 13 Claims. (Cl. 214-14) This invention relates to apparatus for maneuvering, ie., holding, positioning or moving, 4a load between two stations which are subject to relative movement between each other. This invention is particularly useful in maintaining a constant position or constant velocity of a load 'being held or transferred between a floating vessel and another station such `as a dock, another iloating vessel, an underwater structure, the bottom of the sea, or any other selected reference point.

The present invention is an improvement over apparatus of the general type disclosed yand bro-adly claimed in a United States patent application, Serial No. 253,809 entitled Load Maneuvering Apparatus, and filed concurrently herewith by W. C. Carl and H. Zollinger, and .assigned to the same assignee.

When a load is being lifted from a ships deck by a crane Vlocated on the dock, if the crane operator misjudges the .ships position due to wave movement yand hoist speed, the ship may rise on the wave and hit the load before it is clear. On the other hand, when a load lis being placed on the ship the operator must try to judge the roll and pitch of the ship, or the load may hit the deck too hard. In either case damage to both the load and ship is possible.

lFor convenience, the station on which the load moving apparatus .such as a crane is located, will be referred to as the active station, while the other station will be referred to as the passive station. In the ship and dock example, the dock is the active station if the crane is on the dock. The ship in that case is the passive station.

The present invention contemplates apparatus for controlling the movement of .a load between two stations to control the load to desired instantaneous position and a constant velocity relative to the passive station while the stations are subject to relative movement between each other. This may include the case where the desired constant velocity is zero, in which case the Iposition of the load is held constant relative to the passive station.

In the above-mentioned concurrently filed case, there is disclosed load transfer apparatus controlled in response to the difference between the actual and desired speeds of relative movement between the load and the passive station, tha-t is that station to or from which a load is being moved by apparatus on another station. This is effected in the specific embodiment described in that case by resultant control forces produced from a desired load speed signal, an actual load speed signal, and a signal which is proportional to the speed of the relative motion between the stations. Accuracy and speed of response yare signiicantly increased in accordance with the present invention by controlling load trans- 'fer apparatus in response to the diierence between .actual and desired speeds of relative movement between the load and the passive station and the difference between the actual and desired instantaneous position of the load This is efiected generally under the invention by control in response to the difference between the actual and desired speeds of relative movement between the load and the passive station and the integral of this difference thereby providing both speed and position error control.

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In accordance with one embodiment of the present linvention this is accomplished by summing in the input circuit to an operational amplifier, a signal representing desired speed of load relative to the passive station, a signal representing the actual load speed relativeto the active station, and a signal representing the speed of relative motion between the stations, then feeding the output of the amplifier back to its input through an integrating feedback circuit, and employing the bidirectional output of the amplifier to control a bidirectional supply circuit to a reversible load transfer motor.

It is therefore an object of the present invention to provide in apparatus of the character described, improved means for compensating for the relative motion between two stations between which a load is being positioned or transferred.

Another object of the invention is to provide improved apparatus for transferring a load between two relatively moving `stations at a constant desired velocity relative to the passive station.

Another object is directed to substantially eliminating the effect of relative motion between two load transfer stations on the velocity of the load relative to the passive station.

A further object is to maintain a desired position of the load relative to the passive station.

Other objects and advantages of the present invention will be apparent from the following description taken in connection with the accompanying drawing, wherein there is illustrated a preferred form of the invention as embodied in a hoist system for transferring loads between a dock and a tioating vessel.

'ln the drawing there is shown a diagrammatic representation of a crane 10 mounted on a dock 12 for transferring a load 14 between the dock and a floating vessel 16. The crane includes a load lifting cable 13 reeved around a sheave 2li on the outer end of a boom 22 and reeled on a drum 24 driven by reversible drive 26. The drive 26 includes a motor 28 mounted on the crane and a control system 3G for controlling the speed and direction of the motor, :and thereby of the load movement.

By way of example the motor 28 is shown as a direct current motor, and the -control system therefor is shown as including a reversible power supply 32 for supplying power to the motor, and a control network 34 for .controlling the power supply 32 in response to errors of relative position and the speed of relative movement between the load 14 and the ship 16. The power supply 32 shown by way of example includes a generator 36 with a main field 38 excited by a reversible output amplifier 40 controlled by the control network 34. The control network 34 includes a summing and integrating arrangement in the form of an operational amplier 42 with an integrating feedback 44 therearound, and sources of various control signals supplied to the summing input of the operational amplifier.

The armatures of the motor 28 and generator 36 are connected in a loop circuit Si) which also includes series andY commutating iields 52 and S4 of the generator, a. motor commutating iield S6 and a dropping resistor 58 for sampling the `armature current in the loop S0. Motor 28 has a shunt field 6i) connected to a suitable D.C. source. Generator 36 is part of an MG set including a motor 62 which drives the generator. By way of example, motor 62 is shown as an A.C. motor connected to a suitable three-phase A.C. source.

The direction and speed of rotation of motor 28 is dependent on the polarity and amplitude respectively of the voltage output of generator 36. Motor 62 drives the generator at substantially constant speed, and the polarity and amplitude of the generator output are controlled and adjusted by controlling the polarity and amplitude of the voltage supplied to the generator field 38 by the bidirectional amplifier 40. y

Amplifier 40 is of the type which provides a reversible output `having a polarity and magnitude dependent on the polarity and magnitude ofthe net input to the amplifier. In response toan input signal of one sense the amplifier provides an output of one polarity while an input of opposite sense provides an output of opposite polarity. The amplifier is provided with input terminals 70 and 72 which receive input signals along lines 74 and 76 from the control network 34 as amplified by a bidirec-v tional amplifier 80.

By way of example amplifier 40 is shown as having two single-ended channels 82H and S21. whose outputs are oppositely poled across Vthe common output terminals 83 and S4. The inputs of amplifiers 82H and 82L are connected to ,the common input terminals ifi and 72 in an arrangement whereby a common signal of a given polarity along lines '74 and '7o-of a given polarity affects both amplifiers in opposite manner, that is, a signal of a particular polarity drives one of the amplifiers up while tending to drive the other amplifier down or deeper into cutoff, and

Vvice versa in response to a signal of opposite polarity.

With both amplifiers biased to cutoff at quiescent, a signal `of given polarity turns one amplifier on and holds the other amplifier off or turnsit off as the case may be. Since the exemplary arrangementnof amplifiers 82H and 32L is such that the output of amplifier 82H is in a direction to ultimately cause motor 28 to rotate in the hoist direction, and the output of amplifier SZL is of the polarity which ultimately causes motor 28 to rotate in the lowering direction,

et winding and indicate that current flowing intoV the dotted end of the winding as a result of positive voltage applied to that end of the winding tends to drive the magnetic amplifier in the gating generator`98 toward positive saturation thereby tending to increase the output of the amplifier. On the other hand, current entering the undotted end of a winding as aV result Vof positive voltage applied to that end of the winding tends to drive'the magnetic amplifier toward negative saturation thereby tendingY to drive the amplifier downward toward cutoff or further into cutoff as the case may be (depending on operating or bias point). Windings 1151-1 and 116L are connected in series with eachother and across the input terminals 70 and '72 connected to lines 74 and 76Vof the control network34 output lines. As indicated by the polarity dots, windings 11M-I and 1ML have'oppositely related effects on their respective associated gating circuits 93H and 981. in response to a signal of given polarity applied across input terminals '70 and 7,2. A given input signal will drive one Vof the amplifiersup while driving the other one down or further into cutoff. Thus windings 11611 and 116L may be variously referred toas being oppositely poled, or in series opposition,` or in push-pull relation to a common Y f sive to the voltage drop across resistor 58 which in turn Ais responsive to the armature current in the loop t). Thus amplifiers 82H and 32L are labeled hoist and lower amplifiers respectively, and corresponding components in both amplifiers are indicated by the same reference nu- .ineral sufiixed however by the letter H for L to indicate their association with either the hoist or lowering amplifier.

Each of amplifiers 82H and SZL includes two sections, a converter section 86 having gate controlled switching devices 88, 90, 92 and 94 connected in a full wave rectifier bridge arrangement 96, and a firing circuit section 98 for .producing gating signals which are applied to the gating circuits of devices 88, 90, 92 andV 94 to condition the switching devices to fire at a desired phase angle in response phase commutation by alternating current supplied to the input of the bridge.

Devices 88, 90, 92 and 94 are of the type which have a conduction state responsiveto a gating signal, for example,

silicon controlled rectifiers as shown. Across one diagonal thereof, the bridge 96 is provided with A.C. input terminals 100 and 102 to which is connected the secondary .of a transformer 104 whose primary is connected to a source of alternating current 106. The bridge 96 is further provided with positive and negative D.C. output terminals 108 and 110 respectively. The D.C. output terminals of the bridge also constitute the output terminals of the amplier 82. v

To provide the proper operating time relations, the gate signal generator 98 is supplied with alternating current input power along lines 112 from the A.C. source 196 which also supplies transformer 104. The gate signal generator 98 produces output pulses on four output lines 114 whose (pulses) phase positions are determined by the output of a magnetic amplifier included in the generator 98. Each output line 114 is connected to a different one of the switchingY devices 8S, 90, 92 and 94. In lturn the output of the magnetic amplifier is determined by its core saturation. Included in the signal generator 9S are control windings 116, 11S and 120 which control the degree of core saturation in the magnetic amplifier in `accordance with the summation of signals applied to the windings 11811 and MSL constitute current feedback windings providing current negative feedback to form a current regulated system for improved stability.

Windings H and 1201. are damping negative feedback windings. They are oppositely poled in series and together are across a rate feedback network12i connected in the output circuit of the power supply 40 to respond to the rate of change lof power supplied to the generator main field winding 3S. Reactors 130 and 132 are con- Vminals 108H and 110L respectively. These reactors limit the circulating current `due to the instantaneous difference ofthe output voltage of amplifiers 82H and 821..

It should be understood that each of the windings`116, 118 and 12@ may represent onevor more windings tending toward the same result in the associated amplifier.'V

According to the convention adopted herein, when the magnetic amplifier in the gating circuit 98 is driven to some degree of saturation in response to a positive signal applied to the dotted end of the input winding 116, firing pulses are provided on output lines 114 connected respectively to switching devices da, 9e, 92 and 94. When the magnetic amplier is driven up by an input signal on winding 11d, the gating circuit 98 provides gating "pulses to the devices 8d, 90,92 and 9d so synchronized vthat devices 88 and $4 fire at a selected angle during onehalf cycle of the A.C. supply While devices 90 and 92 vthe firing angle, which is determined by thedrive of the magnetic amplifier. y

The type of amplifier shown by way of example for amplifier 32 is described in greater detail in the copending U.S. patent application, Serial No. 43,515, filed on luly 18, 196() by Emil T. Schonholzer, .and assigned to the same assignee as the present application. The reversiblepower supply'SZ is's'hown and described in greater detail in AIEEPaper No. DP62-10l9 entitled Semiconductor Con-trol for Excavating Equipment, and presented by A. M. Vance at the AIEE Empire Tri-District, Erie, Penn- Sylvania, on May 16, 1962, and in a similark article in the July 1962 issue of Mechanization, pages 37-42.

The polarity and response relations of the reversible power supply 32 are so arranged that a positive signal applied to the input terminal '72 will drive amplifier 82H to supply power to the generator main field winding 3S in the proper direction to cause the hoist motor 28 to rotate in the hoisting direction. On the other hand, a negative signal applied to input -terminal 72 drives amplifier 2L to apply power to the generator main field winding 38 in such direction as to cause motor 2S to rotate in the lowering direction.

rihe control network 3d includes a command or desired speed signal source, 141i, an actual load speed signal source 142, a ships motion signal source 144, a summing circuit, for example operational amplifier d2, for summing these signals, an integrating arrangement, for example the integrating feedback 4A; around amplifier d2, for integrating the summation of these signals, and amplifier Sti for amplifying the sum and integration.

The signal source 141i supplies to the summing circuit a desired speed reference or command signal A, representing a desired direc-tion and speed of the load 1d. In the command signal source 14d there is a split potentiometer 1@ connected across a D C. source, tor example the battery shown at 152. A fixed center tap 15d on the potentiometer is connected to a common input terminal 15d of amplier 4t2. The potentiometer 156i is provided with a movable wiper contact 153 mechanically linked to a master controller' handle 161i, and electrically connected to an input terminal 162 of amplier d2. The controller vhandle 16d also operates a drum switch 154 in unison with the potentiometer arm 158.

When the potentiometer arm 15? is moved to the hoist side (right of tap 154) bythe control handle 165i, a positive voltage is applied to terminal 152. On the other hand, when the arm 158 is moved to the lowering side, (left of tap 154) a negative voltage is applied to terminal 162. The magnitude of the output voltage of source 149, adjustable by means of hand-le 16h, is selected to correspond to the desired speed of the motor and hence load movement .relative to the ship (passive station). Thus the speed and direction of load movement relative to the passive station will be dependent on the magnitude and polarityA respectively of the voltage supplied by source 1421?, which in turn is dependent on the position of the potentiometer arm 153 as determined by the handle 160.

A signal B, representing the actual speed of the load 14 relative to the crane 1d, is injected into the summing circuit by a D C. tachometer 1452, which is mechanically conpied to the output shaft 166 of the hoist motor 28. This tachometer provides an output voltage with a magnitude proportional to the motor speed and a polarity dependent on the direction of motor rotation. ln the particular arrangement shown, .and as indicated by the legends over the tacho-meter 14,2, the tachometer generates a positive voltage at its output terminal 163 when the hoist motor 2S is hoisting, and a negative voltage at terminal 163 when the hoist motor E3 is lowering. Output terminal 163 of -tachometer 142 is connected to the common input terminalilid oi the summing amplifier t2 While the other output terminal 171B of the tachometer 142 is connected to a summing input 1712 lof lamplifier d2.

rhe ships motion reference'source ldd, when connected into the summing arrangement by a switch 17d, supplies to the summing circuit a signal C, which is proportional to the velocity of the relative vertical movement between the ship 15 (passive station) and the crane 10 (active station). Source 1414 may, for example, be the tachometer shown and mechanically driven by a drum 176 rotatably mounted on the crane boo-m 22. Common shafting 17S, through which the tachometer 144 is driven by the drum 17 o, is also coupled to the rotor shaft of a torque ymotor isti. The torque motor may be ofthe type having a wound rotor with adjustable roto-r resistors to adjust the torque. Attached to and wound around -the drum 17o is a length of cable 182 the free end of which is fixed to the ship at 184, for example by merely attaching sufficient weight to the end of the line to hold the line in tension against the torque of the torque motor 130. As the ship rises and falls, the free end of the line at 134 remains fixed relative 4to the ship while the rest of the line is held at constant tension as it winds and unwinds `on and oft the drum. Thus, the tachometer 144 is rotated in one or the other direction depending on the direction of the vertical motion of` the ship, and in response to such rotation the tachometer generates a voltage of one or the other polarity depending on the ships movement. The polarity of such a signal will be dependent upon the direct-ion of the relative movement between the vessel and the dock, while the magnitude of the signal will be proportional to the speed of such relative movement. In the specific arrangement shown by way of example, and as appears in the legends underneath the tachometer 144, this tachometer produces a positive voltage at its output terminal 186 when the ship is falling (as into a wave trough), and a negative voltage at terminal 186 when the ship is rising (as onto the crest of a wave).

It should be appreciated that this is a diagrammatic showing for ease of illustration, and that as a practical matter the tachometer 144, the drum 176, and the torque motor 18) would be located on the crane platform while the cable 182 is passed around a pulley on the boom.

he output terminal 186 of the tachometer `14d is connected to the common input terminal 156 of amplifier 42, while the other voutput terminal 183 of the tachometer 144 is connected to the arm of switch 174, the other contact 19t? of the switch being connected to a summing input terminal 192 of the summing amplifier 42.

Amplifier 42 may be any suitable summing D.C. amplier. For the most accurate results, it is most desirable that the amplifier 42 be as drift free as possible. To this end and by way of example, amplifier 42 is shown as a chopper stabilized D.C. operational amplifier. Chopper stabilization is accomplished in the well known manner by means of an A.C. amplifier and chopper as shown at Zitti. The output of amplifier 42 appears at output terminals 292 and 204 .and is applied for further amplification to amplifier Si), whose output appears on lines 74 and 75 as the output of the control network 34. The feedback integrating network 44 is connected from the output terminal 262 to an input terminal 297 of the amplifier 42 so that the output of amplifier 42 appearing on its output terminals 202 and 204 includes the summation of the input signals and also the integral of the summation of these signals. The integrating feedback circuit 614 includes a capacitor 263 and a resistor 210.

With the capacitor 20S connected as shown, and resistors being connected as shown in the various input lines to the amplifier input, the operational amplifier performs as an integrator which provides an output that is proportional to its input plus the integral of its input.

The polarity relations of the various signals supplied to the summing circuit are such that the command or desired speed reference signal A from the command source 149 for any given command direction is opposed in the summing circuit by the actual motor speed signal B produced by the tachometer 142 vwhen the motor is rotating in the command direction.

With the switch 174 closed, the ships motion reference tachometer 144 supplies a signal C to the summing circuit which aids the command signal A from the source 14d when the relative movement of the ship and the crane is in the direction tending to oppose the purpose of the command signal A, and which signal C opposes signal A when the direction of relative movement between the ship and the crane aids the purpose of the command signal A. It should be apparent that a falling ship opposes the purpose of a lowering command, while a rising ship aids the purpose of a lowering command. Also, a hoist command is opposed by a rising ship, and aided by a falling ship. These relations reverse when the-posik'disagree vtion of the crane is reversed, that is when the crane is on the ship. In the latter case a dipping crane boom aids the purpose of a lowering command, while a rising crane boom opposes the purpose of a lowering command. Also, with the crane on the ship, `a hoist command is aided by a rising crane boom, and opposed by a dipping crane boom.

The summing circuit 4t2 is so arranged that a positive signal on any of summing input terminals 172, .to2 and 2&92 tends to produce a positive signal on the output line L76 and thereby on the input terminal 72 of the reversible amplier 46. As stated before, this would tend to drive the motor 28 in the hoist direction. On the other hand, a negative signal at any lof the input summing terminals 23.72, ftd? and X92 will tend to produce a negaintegral of the summation.

The output shaft ofthe hoist motor T28 is provided ,with an electrically rcleasable spring set shoe brake 22 which remains set while the master controller handie lh is in neutral or a switch 222 is in the open position. Y

However, when the controller le@ is moved to either ythe -hoist or the lower position, the brake energizing circuit 2924 connected to the brake 22o energizing coil is closed by one or the other of a pair of drumV switch segments 2.26 and 22S which are adapted to short a set of contacts y 23h in the brake energizing circuit.

The circuit includes a relay ZSZ'and a battery 234, which operates the relay 232 in response to either closing of switch 222. or the shorting of contacts 23d by the drum switch segments. In response to operation of relay 232 relay contacts 23o are closed to energize the brake coil with battery 23d voltage thereby releasing the brake.

Switches 174 and 222 are ganged to open and close together in response to the movement of .a lever 24d, which when moved to MAN. (manual) position opens switches 222 and i741, and when moved to AUTO. (automatic) position closes these switches. ln the manual position of lever 24.0, the brake energizing circuit is open as long as -controller handle lo@ is in the neutral position. Also in the manual posi-tion of handle Zilli, switch t7@ being open, the ships motion reference signal is not injected into the summing circuit. Operating under these conditions, only the command signal A from the command source 14o and the actual speed signal Btrom the Y this operation, to loweror hoist the controller handle` lo@ must be moved to lower or hoist position.

Operation wit/zou! the slzz'ps motion reference As hereinbefore stated the command or desired speed reference signal A from the command source le@ for j `any given command direction is opposed in the summing Vcircuit 42 by the. 'actual motor speed signal B produced by the tachometer M2. The magnitude and polarity of the command signal A from the command source i4@ is depend-ent on the desired speed and direction of,

is moved into the hoist sector of the controller range to a selected position corresponding to the desired speed.

Movement of the handle lo@ Vinto the hoist sectorY moves the drum switch lof-l and the potentiometer arm 153 in unison to the right or the hoist sector of the controller. in this sector, the potentiometer arm i555 taps into the positive side of the potentiometer litlrto provide a positive polarity command signal A to the summing 'input of the'ampliiier 42, the magnitude of the signal corresponding to the selected command speed. This drives the output of ampliiier t2 positive at terminal d2 and positive at the input terminal 72 of the reversible am-` pliier 4d, thereby turningthe hoist ampliiier 82H on and turning the lowering amplifier dfi oit, thus energizing the generator mainiield winding 33 to drive the hoist kmotor 28 in the hoist direction. As the speed of -the hoist motor increases, the output voltage of the tachometer to2 which is opposed to the command signal, `increases until equilibrium is reached, wherein enough excitation is supplied to the motor to produce the requisite torque to maintainrthe selected command speed.

if for any reason the motor 23 should run faster than the command speed, the tachometer MZ voltage will be greater than the command signal A and the polarity of vthe resulting error signal will be such as to apply positive voltage to the input terminal 7@ of the reversibleV amplifier ftd. This results in the lowering amplifier 8.2L being driven on and the hoist amplier 32H being driven ott, the net result being an application Vof regenerative braking, ythus slowing the motor down until equilibrium by vto rotate the motor `in the lowering direction.

inthe lowering direction, tachometer ML2 produces an output volt-age which is positive at the terminal 172 thereby opposing the command signal'A which for the .lowering direction is negative. A-s the speed of the load increases in the lowering direction, the tachometer M2 output voltage increases. lf the lowering of the load tends ot overhaul the motor, the tachometer M2 voltage ywill exceed the command signal A thereby causing amplier 42 to produce an output which tends to drive the hoist ampliiier 32H on and the lowering amplifier S21. off to provide suilicient regenerative torque to keep the overhauling load at -the command speed. f

in this mode of operation (lever .2d-ti in the manual position) the load movement is maintained at a constant speedrela-tive to the crane 22 and dock l2 for a given command speed. Although the load speed is constant relative to lthe crane and crane support (active station), the speed of the load relative to `to the ship (passive station) is undesirably variable due to the rise and fall ofthe ship because of wave action.

Operation with the ships motion signal To substantially eliminate the effect of the ships motion, the ships motion reference signal C from the tachometer ldd is added to the summingcircuit d2 by closing switch 17d.

As he-reinbefore stated, the polarity relation of the ships mot-ion reference circuit ldd to the rest of the 'summing circuit is such that the command signal A from the desired speed reference source Mtl and the slu'ps motion signal C from the ships motion reference source ldd in the mutually aiding relation when the direction of relative movement between the ship and the crane is opposite to the commanded direction of relative movement between the load and the ship. In other words, vior this circumstance, the signals A and C have similarly sensed control eitect on the controi system Sti. On the Vas the commanded relative movement between the load and the ship. For example, when the ship is rising, that is, when the direction of the relative movement between the ship and the crane is in the closing direction, the ships motion tachometer ldd provides a positive output `on terminal M2 of the summing circuit. However, when the ship is falling that is, when the relative movement between the ship and the crane is in the opening direction, the output of the ships motion tachometer 14d is negative at terminal i192.

The operation of the crane example will now be considered in more specific detail. Suppose that a load is to be transferred yfrom the docli to the ship. With the lever 24d in the manual position (switches 174 and 222 open), the crane operator swings the crane 22 around its vertical pivot to a position over the load on the dock. rl`he'load is hooked to the line li and the crane operator raises the load by operating the master control lieti to the hoist side. This releases the brake 22@ and hoists the load. At a particular hoisted position, the load may he held by moving the control lo@ to neutral thereby setting the brake and setting the command signal A at Zero voltage whereby the regulator regulates for zero speed. The crane is then swung around its vertical pivot to position the load over the ship. At this time, the tag line iti?. may be unwound from the drum 17o and lowered to the ships deck by proper use of a reversing switch 254B in the supply lines of motor llh?. Once the line 132 is ixed to the ships deck, the reversing switch $350 is operated to reverse the motor lidi) and the torque motor control circuits are adjusted to apply just enough torque to maintain constant tension on the line ltl. In a wound rotor motor, this adjustment may be made by adjusting the secondary resistance. Next the operiator moves lever Zet) to the automatic position thereby closing switches 174 and 222. rPhe drive system now will follow the ships motion signal and maintain a constant distance between the load and the ship. A special use or" the invention may be for this purpose alone, that is, to hold the position of a load constant with respect to the passive station. For example the load may be an object carried by a ship, which object needs to be held in constant position relative to the sea bottom.

In order to lower the load to the ships deck, the crane operator moves the master control lo@ to the lowering side to provide a lowering command signal A which is negative at the input terminal of the summing amplier. The ultimate result is to drive the lowering ampliier 321, on and cause the hoist motor 28 to rotate in the lowering direction. As the load starts to move down, the speed feedback tachometer T142 puts out a positive signal at the input terminal i722 to the summing circuit which opposes the command signal A. lf in the meantime the ship is rising, the ships movement tachometer 144i, generates a positive signal at the input terminal 192 to the summing circuit which opposes the command signal and forces the drive to run slower. If, as the ship is rising, the ships movement tachometer signal C exceeds the command signal A, the load will actually he hoisted. On the other hand, if, as the load is being lowered, the ship is falling, the ships movement tachometer 144 output signal C will be negative at the input terminal thus aiding the command signal A thereby causing the drive to lower faster. Thus the application of the ships motion signal C to the regulating loop regulates the drive to maintain not only a constant speed between the load 14 and the ship lr6 for any selected command speed but also, due to the integrating feedback circuit 44, it regulates the drive to maintain a correct instantaneous position between the load and the ship.

When it is desired to lift the load from the ship, the

l@ crane operator moves the master controller 16d to the hoist position applying a positive command signal to the summing circuit thereby driving the hoist amplifier 82H on and causing the hoist motor 28 to rotate in the hoist direction.

As the load rises, the speed feedback tachometer 142 generates a negative signal to the summing circuit at terminal IN2, tending to cancel the command signal A to keep the drive at a constant speed relative to the dock. if the ship rises as the load is being hoisted, the ships movement tachometer 144 generates a positive signal at the summing circuit input terminal 192, thus aiding the command signal and forcing the drive to hoist faster, thereby to maintain constant hoisting speed between the load le and the ship lo.

As seen from the description herein, the present invention makes the motor 23 hoist or lower at a speed necessary to keep the load moving with respect to the ship, at the speed set by the master control regardless of the up and down movement of the ship.

It should be noted that the summation of the reference command signal A, the actual speed signal E and the ships motion signal C produces an error signal which is responsive to the diierence between the actual and desired speeds of relative movement between the load 14 and the ship lo (passive station). Additionally, the integrating arrangement 44 provides the integral of the difference between the actual and desired speeds of relative movement between the load and the passive station, thus providing a regulating signal with both speed and position error components on the output lines 74 and 76, by which the drive system is controlled.

Although above water stations have been illustrated, the invention is also very useful in the case where a hoist on a vessel iloating on the surface of the water lowers and hoists objects to and from an underwater station such as the bottom of the sea, an underwater structure, or any selected underwater reference level. The invention helps to reduce the effects of sudden load changes on the hoist equipment due to the friction or retarding effects of the water on the load as the ship rises and falls with the Waves or swells.

The invention is not limited to hoists, but may be used for other purposes, for example to hold a load (any object), that is movable by appparatus on an active station, to a desired instantaneous position relative to a passive station when relative movement is going on between the stations. In such a case the value of the desired velocity of relative movement between the load and the passive station is zero.

The invention is not limited to the particular reversible drive and control therefor shown by way of example. Other suitable reversible drives and controls therefor may be employed in practicing the invention. Likewise the shlps motion signal 192 may be obtained by other suitable apparatus, for example, gyroscopic systems, sonar systems, radar, or any other apparatus which will provide a signal responsive to the relative movement between two bodies. Thus, it is to be understood that the hereindescribed arrangements are simply illustrative of the principles of the invention, and other embodiments and fabrications are within the spirit and scope of the invention.

We claim as our invention:

l. ln apparatus for maneuvering a load between two stations which are subject to relative movement between each other, and wherein there is an adjustable speed reversible drive means for moving the load, said drive means including motor means located on one of said stations for moving the load, the combination therewith of Iirst control means responsive t-o the difference between actual and desired speeds of relative movement between the load and the other station for produc-ing a first signal component proportional to that diterence, second control means responslve to the difference between actual and desired instantaneous positions of the load relative to the :risorsa il other station for'producing av second :signal component proportional to the last said difference, and means coupled to said drive means and vto said rst and second control means for controlling said drive means in response to said iirst and second signal components to maintain a desired speed of relative movement between the load and the other station while relative movement is going on between said stat-ions.

12.V In apparatus for maneuvering a load between two Vvstations which are subject to relative movement between each other, and wherein there is an adjustable speed reversi-ble drive means for moving the load, said drive means including motor means located on one of said stations for moving the load, the combination thercwvithV of control means for controlling said drive means, said control means 'comprising means providing a first signal proportional to the difference between actual and desired speeds of relative movement between the load and the other station,

'means responsive to said iirst signal for producing a second signall which is proportional to the first signal and the integral thereof, and means responsive to said sccond signal for causing said drive means to maintain a de- 'isired speed of relative movement between the load and the other station. Y

v3. In apparatus for kmaneuvering a load between two 'stations which are subject to relative movement between each other, and wherein there is an adjustable speed reversible drive means for moving the load, said drive means including motor means located on one of said stations for moving the load, the combination therewith ci means for providing a command signal A indicative of adesired speed and direction of movement of said load relativeto the other of said stations, means for providing a signal B dependent on the .actual speed ofV the load relative to said one station, means for providinga signal C dependent on the speed andV direction of said relative movement between said stations, a summing circuit in which said sig- Vnals A, B and C are summed to produce a signal comeach other, and wherein there is an adjustable speed rel versible drive means for moving the load, said drive means including motor means located on one of said stations for moving the load, the combination therewith of means for providing a command signal A indicative of ya desired speed `and direction of movement of said load relative to the other of said stations, means for providing a signal B dependent on the actual speed of the load relative to said one station, means for providing a Signal YC dependent on the speed and direction of said relative motion between said stations, a summing circuit in which said signals are summed to produce a signal summation proportional to the difference between the actual and desired speeds of relative movement Ibetween said load `and said other station, circuit means coupled to said surnrning circuit and responsive to said signal summation for lproducing an output having. a component proportional to said summation an-d a component proportional to the integral of said summation, and means coupled to said circuit means and said drive means for controlling said drive means in response to said output of said circuit means to maintain said desired speed and direction of movement of said load relative to the other of said stations.

5. ln apparatus for maneuvering a load between two stations which are subject to relative movement betweenv E fr each othcnand wher 'n ti ere isan adjustable speedreversible drive means for moving the load, said drive means including motorV means locatedon one of said stations for moving the load, the combination therewith of means ror providino a command signal A indicative of a desired speed and direction of movement tive to the other of said stations, means for providing a signal'B dependent on the actual speed of the load relative to said one station, means for providing a signal C dependent on the speed and direction of said relative motion bctwee said stations, an operational ampliiier having an integrating Vfeedback circuit therearound and a summing input to which said signals are applied, said summing input providing a signal summato'in that is proportional to the difference betweeny the actual and desired speeds of relative movement between the load and said other station, said amplifier providing an output that is i proportional to said summation and the integral of said summation, anda control cricuit coupled to said amplilier and' to said drive means and responsive to said ampliiier output for operating said drive means to maintain viding a signal B dependent on the actual speed ot they load relative to said one station, means for providing a signal C dependent on the speed and direction of said relative motion between said stations, an integrating summing circuit havng an output circuit and an input circuit to` which said signals are applied, vsaid,integrating vsumming circuit being arranged to produce an output which is proportional to both the summation oi the sig- 'nals applied` to its input and the integral of that summation, and control means coupled to said drive means and the outputcircu-it of said integrating summing circuit and responsive to said output of the integrating summing circuit for operating said drive circuit to maintain said desired speed and direction of movement of said load relative to said other station.

7. In apparatus for maneuvering a load between two stations which are subject to relative movement between each other, and wherein there is an adjustable speed reversible drive means for moving the load, said drive Vmeans including motor means located on one of said stations for moving the load, the combination therewith of means for providing a command signal A indicative of a desired speed and direction oi movement of said load relative to the other of said stations, means for providing `a signal B dependent on the actual speed ofthe load relative to said one station, means for providing a signal C dependent on the speed and direction of said relative movement between said stations, a control network that includes summing means and integrating means and provides an output which is proportional to the summation of its input signals and the Vintegral of that summation, means for applying said signals A, B and C as input signals to said control network in such relation that said summation produced by said control network `is proportional to the diiierence between actual and desired speeds of relative movement between said load and said other station, and means coupled to said control networlr and to said drive means for controlling said drive means in response to said output of the control network to maintain said desired'speed and direction of movement of said load relative to said other station.

8. Inapparatus for maneuvering a load between two stations which are subject to relative movement between of said load rela- V,

13 e'ach other, and wherein there is an adjustable speed reversible drive means for moving the load, said drive means including motor means located on one of said stations for moving the load, the combination therewith of means for providing a signal B dependent on the actual speed of the load relative to said one station, means for providing a signal C dependent on the speed and direc ion `of said relative motion between said stations, a control network that includes summing means and integrating L means and provides an output which is proportional to the summation of its input signals and the integral of that summation, means for applying said signals B and C as input signals to said control network, and means coupled to said control network and said drive means for controlling said drive means in response to said output ofthe control network.

9. In apparatus for maneuvering a load between two stations which are subject to relative movement between each other, and wherein there is an adjustable speed reversi-ble drive means for moving the load, said drive means including motor means located on one of said stations for moving the load, the combination therewith of means for providing a signal B dependent on the actual speed of the load relative to said one station, means for providing a signal C dependent on the speed and direction of said relative motion between said stations, a summing circuit in which said signals are summed, said summing circuit producing a summation signal representing the sum of signals B and C, integrating means coupled to said summing means for producing an integration signal representing the integral of said sum, and control means responsive to said summation and integration signals for operating said drive means.

v10. In apparatus for maneuvering a load between two stations which are subject to relative movement between each other, and wherein there is an adjustable speed reversible drive means for moving the load, said drive means including motor means located on one of said stations for moving the load'fthe combination therewith of means for providing a signal B dependent on the actual speed of the load relative to said one station, means for providing a signal C dependent on the speed and direction of said relative motion between said stations, an operational ampliier having an integrating feedback circuit therearound and a summing input to which said signals are applied, said operational amplifier being arranged to 14 provide an output that is proportional to its input and to the integral of its input, and a control circuit coupled to said amplier and said drive means and responsive to said amplifier output for operating said drive means.

1'1. The combination as in claim 3, wherein said signals are related as follows: signal B is negative feedback relative to signal A, signals A and C aid each other when the relative movement between said stations is opposite to the commanded relative movement between the load and said other station; and signals A and C oppose each other when the relative movement between said stations is in the same direction as the commanded relative movement between the load and said other station.

12. The combination as in claim 5, wherein said signals are related as follows: signal B is negative feedback relative to signal A, signals A and C aid each other when the relative movement between said stations is opposite to the commanded relative movement between the load and said other station, and signals A and C oppose each other when the relative movement between said stations is in the same direct-ion as the commanded relative movement between the load and said other station.

l113. The combination as in claim 7, wherein said signals are related as follows: signal B is negative feedback relative to signal A, signals A and C aid each other when the relative movement between said stations is opposite to the commanded relative movement between the load and said other station, and signals A and C oppose each other when the relative movement between said stations is in the same direction as the commanded relative movement between the load and said other station.

References Cited bythe Examiner UNITED STATES PATENTS 709,915 9/02! Leonard 214-13 709,916 9/02' Leonard 214-13 2,293,936 8/42 Crooke 212-3 X 2,832,024 4/58 Wickerham 318--229 2,854,154 9/58 Hepinstall 214-14 2,946,466 7/60 Weiner 214-14 3,088,710 5/63` Evans et al. j 254-172 HUGO O. SCHULZ, Primary Examiner.

GERALD M. FORLENZA, Examiner. 

1. IN APPARATUS FOR MANEUVERING A LOAD BETWEEN TWO STATIONS WHICH ARE SUBJECT TO RELATIVE MOVEMENT BETWEEN EACH OTHER, AND WHEREIN THERE IS AN ADJUSTABLE SPEED REVERSIBLE DRIVE MEANS FOR MOVING THE LOAD, SAID DRIVE MEANS INCLUDING MOTOR MEANS LOCATED ON ONE OF SAID STATIONS FOR MOVING THE LOAD, THE COMBINATION THEREWITH OF FIRST CONTROL MEANS RESPONSIVE TO THE DIFFERENCE BETWEEN ACTUAL AND DESIRED SPEEDS OF RELATIVE MOVEMENT BETWEEN THE LOAD AND THE OTHER STATION FOR PRODUCING A FIRST SIGNAL COMPONENT PROPORTIONAL TO THAT DIFFERENCE, SECOND CONTROL MEANS RESPONSIVE TO THE DIFFERENCE BETWEEN ACTUAL AND DESIRED INSTANTANEOUS POSITIONS OF THE LOAD RELATIVE TO THE OTHER STATION FOR PRODUCING A SECOND SIGNAL COMPONENT PROPORTIONAL TO THE LAST SAID DIFFERENCE, AND MEANS COUPLED TO SAID DRIVE MEANS AND TO SAID FIRST AND SECOND CONTROL MEANS FOR CONTROLLING SAID DRIVE MEANS IN RESPONSE TO SAID FIRST AND SECOND SIGNAL COMPONENTS TO MAINTAIN A DESIRED SPEED OF RELATIVE MOVEMENT BETWEEN THE LOAD AND THE OTHER STATION WHILE RELATIVE MOVEMENT IS GOING ON BETWEEN SAID STATIONS. 